The present invention relates, in general, to an overhead transport system for moving loads, and more particularly to a transport system of a type including load-bearing members which travel along running rails extending at least in two horizontal planes in spaced-apart parallel disposition, and a crane which travels in an upper one of the planes transversely to the running rails for transfer of the load-bearing members from one running rail to another running rail.
It is known from the magazine xe2x80x9cMaterialflussxe2x80x9d, April 1982, pages 31-34, to provide a crane assembly with several production planes. A transfer of loads is normally realized by several cranes whereby the loads are suspended from load-bearing members which are provided with running gears. The cranes travel in the upper plane transversely to the running rails and are designed to transfer load-bearing members from a running rail of one plane to a running rail of another plane. In addition to the transfer of the load-bearing members in vertical direction, the cranes also carry out a transfer of load-bearing members between running rails in a same plane. This type of crane assembly suffers shortcomings because a time-efficient operation of the transfer procedures requires the use of several cranes. As a consequence, the overall costs are relatively high; yet the provision of several cranes still fails to effectively reduce the time for carrying out the transfer procedures as cranes of this type are slow in operation.
It is thus an object of the present invention to provide an improved overhead transport system, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved overhead transport system which includes at least two production planes in a cost-efficient manner while still being able to effectively reduce the overall transfer times.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a first rail system positioned in a horizontal plane and including running rails for travel of load-bearing members; a second rail system located in a horizontal plane in parallel, spaced-apart disposition to the first rail system and including running rails for travel of load-bearing members; a crane traveling in an upper one of the planes of the first and second rail systems in a transverse direction to the running rails for transferring the load-bearing members from one of the running rails to another one of the running rail; and a self-propelled transfer vehicle traveling in a lower one of the planes of the first and second rail systems in a direction transversely to the running rails for transferring load-bearing members in the lower one of the planes.
Through the provision of a separate, self-propelled transfer vehicle, the transfer of load-bearing members in the lower one of, for example, two vertically spaced planes does no longer require the use of a crane but is assumed by the much more agile transfer vehicle which is of much simpler structure than the crane, and attain a reduction of transfer times. The crane is thus used primarily used for transfers in the upper plane and for transfers between the upper and lower planes.
The time for transfer of a load-bearing member from and to a running rail can be kept brief, when providing rail elements which are shiftable for alignment with ends of the running rails for receiving at least one load-bearing member from one running rail and transfer thereof to another running rail, with the rail elements being shiftable together with the one load-bearing member. Thus, the load-bearing members travel, for example, from one running rail onto the rail element of the transfer vehicle and can be placed into alignment with another running rail to enable the load-bearing member to travel from the rail element to this running rail. Suitably, at least one of the rail elements is arranged on the transfer vehicle. Thus, the transfer vehicle can then move he desired running rail in position for receiving or transfer of at least one load-bearing member.
According to another feature of the present invention, the transfer vehicle can self-propel to a position adjacent a desired end of the running rail for connection of the rail element with the respective running rail, so that short transfer periods are attained in the respective plane with the transfer vehicle. The time for travel as well as for precise positioning can thereby be kept small.
In a simple configuration, the rail element may be a running rail portion for support and guidance of the load-bearing member. This results in a cost-efficient design, as the running gears can be precisely matched to the shape and size of these running rails. Suitably, the running rail portion is designed rectilinear.
According to another feature of the present invention, the transfer vehicle may include two rail elements in parallel, spaced-apart disposition. This configuration is suitable when long travel paths are involved, as two running rails may be used simultaneously, or the same running rail can be used successively for reducing the travel time.
Suitably, the stability of the rail element can be increased by arranging each running rail on a support beam. The support beam is of massive configuration so that the overall system of support beam-rail element can be supported on both ends of the support beam. A transfer of the rail element by the crane can suitably realized together with the support beam in a same plane or from one plane to another plane. A precise positioning, in particular during placement of a support beam by the crane into the lower plane, can be realized by providing two funnel-shaped receptacles in which both ends of the support beam automatically position themselves.
According to another aspect of the present invention, the load-bearing members are provided with running gears to permit the load-bearing members to self-propel themselves onto the rail element. This may be carried out immediately after connection of the running rails, so as to secure also in this case short transfer times. It is, however, also possible to pull the load-bearing member onto the running rail or to push the load-bearing member from the running rail. This is advantageous because transport assignments can be separated from one another.
According to another aspect of the present invention, the transfer vehicle and/or the crane travel in a corridor, with the running rails being arranged in at least one of the planes at either side of the corridor in a direction transversely to the longitudinal axis of the corridor. As a result continuous running rails are realized during traverse of the transfer vehicle so that aligned running rails, separated only by the corridor, are temporarily connected for through-passage for a load-bearing member.